Duplicating



Patented Apr. 3,1928,

DAVID GESTETNER, OF LONDON,

DUPLICATING.

No Drawing. Application filed June 15, 1923, Serial No. 645,708, and inGreat Britain October 27, 1922.

This invention relates to' duplicating by the employment of flexiblestencils comprising a foraminous support constituted by, for instance,yoshino or like paper and a stencil layer formed of ink-resistingmaterial, and has for its object to provide improvements instencils ofthe character in question.

The invention consists in incorporating in the composition forming thestencil layer an opaque pigment of a tint contrasting with the colourofth'e ink with which the stencil ,is to be used.

Ordinarily, the pigment .will be-an opaque white igment.

Pref eirably, if the stencil layer is a gelatine or like composition apigment is employed which has the elfect, by itself or in combinationwith other constituents of the composition forming the stencil layer, ofraising its liquefying point and improving its qualities in otherdirections as, for instance, its resistance to the destructive action ofthe ink with which it is to be employed,

As examples of pigments which may be employed, white zinc pigments orwhite titanium pigments may be mentioned. The use of the latter appearsto be distinctly advantageous in the production of stencils produced bythe action of light upon a gelatine composition sensitized withbichromate, as it is foundthat this pigment assists in rendering thegelatine'insoluble.

The employment of such pigments in combination with the wax-likecompositions used in forming so-called wax stencils is also of utilityas it would seem that stencils containing pigments are less liable to beaffected by climatic conditions. In this con nection it may be remarkedthat the expression wax-like composition is intended to' includecompositions which have the appearance of /wax, as forinstancecompositions consisting wholly, mainly or in part of soaps.

One of the mostlobvious advantages of the invention arises from the factthat when the stencil sheet is in use the matter which is to bereproduced by its employment is visible. In addition, defects can beobserved in the stencil directly and not merely by observing the resultsof such defects in the duplicates produced by its employment.

The stencil sheet proper is (as is common in the art) convenientlysecured to a detachable backing sheet, the whole being commonly referredto as a-combined stencil sheet.

The purpose of the-backing sheet is mainly to provide a substantiallyrigid or hard support for the sheet in cutting the stencil by means of"a typewriter and the portion of the surface of the backing sheetcorresponding with the portion of the stencil sheet on which the stencilwill be cut is in many cases black, being coated with printing ink withthe ob- ENGLAND, ASSIGNOR' TO D. GESTETNER LIMITED, OF LONDON, ENGLAND.

ject of rendering matter cut in the stencil more easily legible.

The object, however, is not sufiioiently achieved in this way. If,however, the hard surfaced backing sheet is coated with a transferringink over that portion of its surface which corresponds with the portionof the stencil sheet in which the impression is to be cut, the operationof cutting the stencil will cause an impression in' the transferring inkto be produced on the stencil sheet wherever the stencil layer is cutand the" matter cut in the stencil will then be clearly legible.

This, as wi convenience and, for instance, reduces eyestrain on the partof the person cutting the stencil as well as in reading or checking it.

The transferring ink may be an ink similar to the oily or greasy inksused in duplicating; it may, for instance, be an ink'comprisingessentially a pigment suspended in mineral jelly. Alternatively, the inkmay be similar in character to the wax 'and pigment compositions used informing the so-called carbon paper.

The following particulars are given, byway of example, to illustratesuitable modes of carryingthe invention, as applied to the production ofstencil sheets for use in makll be rcb gnized, is of great ing stencilsby cutting with a style orin a' typewriter, into effect:

Ewample I 3 parts of a white titanium oxide pigment such as'a pigmentcontaining titanlum oxide and barium sulphate are added to 50 parts of a20 per cent solution of gelatine to which also 15 parts of glycerine and20 arts of water are added. Yoshino paper is coated with thiscomposition in known manner as, for instance, by drawing, it over aadded to 90 parts of a molten mixture consisting of 40 parts of muttontallow and 50 parts of paraflin wax of in. p. 135 F. and when theproduct is suitably mixed yoshino paper is coated with it in knownmanner.

Ea'wmple HI.

Sheets of a suitably hard-surfaced paper, such as has hitherto been used1n forming the backing sheets of combined stencil sheets,

are provided over the greater portion of the surface of one side (theside which is to be next to the stencil, in cutting the same) with a.coating of an ink formed by intimately mixing 8 parts of lamp-black with100 parts of mineral jelly, by for instance a printing operation. To thesheet thus treated a stencil sheet formed in the manner described ineither of the preceding examples or in any other suitable manner issecured near one edge by means of an adhesive.

Having now described my invention What I claim as new and desire tosecure by Letters Patent is 1. An improved flexible stencil sheet com-DAVID GESTETNER.

